Liquid-cooled turbine bucket

ABSTRACT

Turbine blade construction is described providing for the uniform distribution of cooling liquid to eliminate significant temperature gradients over the blade surface. Each blade consists of a central airfoil-shaped spar clad with a sheet of metal having a very high thermal conductivity e.g. copper. The cladding sheet has grooves recessed in the sheet face adjacent the spar, which grooves together with the surface of the spar define coolant passages distributed over the surface as dictated by the cooling requirements.

United States Patent [72] Inventor Paul H. Kydd Scotia, N.Y. [21] Appl. No. 7.805 [22} Filed Feb. 2, 1970 [45] Patented Nov. 9, 1971 [73] Assignee General Electric Company [54] LIQUID-COOLED TURBINE BUCKET 5 Claims, 3 Drawing Figs.

{52] U.S.Cl 415/115. 416/92. 4 l6/95, 416/96 511 lnt.Cl l-Old 5/14 [50] FieldofSearch 4l5/ll5; 416/90, 92, 95-97 [56] References Cited UNITED STATES PATENTS 3,075,744 1/1963 Peterson A. 415/] l5 3,446,480 5/1969 Emmersonetal. 3,446,48l 5/1969 Kyddetal 4.

Primary Examiner-C. J Husar Alturneys- Paul A. Frank, Richard R. Brainard, Charles T.

Watts, Leo l MaLossi, Frank L. Ncuhauser. Oscar B. Waddell and Joseph B. Forman ABSTRACT: Turbine blade construction is described providing for the uniform distribution of cooling liquid to eliminate significant temperature gradients over the blade surface. Each blade consists of a central airfoil-shaped spar clad with a sheet of metal having a very high thermal conductivity e.g. copper. The cladding sheet has grooves recessed in the sheet face adjacent the spar, which grooves together with the surface ofthe spar define coolant passages distributed over the surface as dictated by the cooling requirements,

PAIENTEDuuv 9 I971 SHEET 1 OF 2 Inventori ozu/fi-l. Kydd,

Wis Attorney.

LIQUID-COOLED TURBINE BUCKET BACKGROUND OF THE INVENTION The evolution of successful techniques for the cooling of gas turbines by the use of liquids as described in U.S. Pat. Nos. 3,446,48ll(ydd and 3,446,482-Kydd (both patents are incorporated by reference) brings into the realm of reality gas turbines operating at peripheral speeds in excess of about 1,500 ftJsec. and at turbine inlet temperatures in excess of about 2,100 F. Such operation necessarily imposes very high heat loads on the turbine buckets and it becomes imperative to avoid temperature gradients over the bucket surfaces caused by this extremely large heat flux.

The problem of turbine bucket cooling in the high temperature turbines referred to the the aforementioned patents are considerably more severe than those encountered in the operation of gas-cooled gas turbines and for this reason, construction features providing for the cooling of buckets in gascooled turbines are inadequate for the cooling of buckets in liquid cooled gas turbines.

SUMMARY OF THE INVENTION Each blade of the instant invention consists of a central airfoil-shaped spar with its outer surface covered with a sheet of metal having a very high thermal conductivity, such as copper. This covering sheet, or cladding, has grooves recessed in the face thereof, which is disposed contiguous with and bonded to the outer surface of the spar. These grooves define coolant passages distributed over and close to the surface of the composite blade as dictated by the cooling requirements. These passages are in flow communication with a supply of coolant liquid at the radially inward terminals thereof, the radially outward terminals thereof being open for the discharge of the coolant.

BRIEF DESCRIPTION OF THE DRAWING The exact nature of this invention as well as objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing in which:

FIG. 1 is a transverse sectional view through a liquid-cooled gas turbine showing the rotor disc supporting a turbine bucket constructed in accordance with this invention;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1 and FIG. 3 is a sectional view taken on line 33 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there is shown part of a gas turbine structure including rotor shaft 11 affixed to the turbine rotor 12 projecting radially from the shaft axis. As shown, rotor 12 is composed of three sections; hub 13, rim section 14 and a tapered connecting section 16 between the hub and rim sections. The rim section 14 has a series of transverse recesses 17 formed therein, each of which receives the dovetailing root 18 of a turbine bucket, or blade 19.

Cooling action is accomplished in accordance with this invention by spraying a liquid coolant, generally water, at low pressure onto the turbine disc from stationary cooling noules 21, 22 supported on stationary annular discs 23, 24, respectively. In the arrangement shown the low pressure water leaving nozzles 21, 22 impinges on the sides of disc 12 in the vicinity of rim section 14 and over the underside of platform portions 26 of each spar 27.

The airfoil-shaped stem 28 of each spar 27 is covered by a sheath (about 0.020 inch to about 0.050 inch thick) of a metal such as copper, having very high thermal conductivity. This sheath or cladding also extends down over the upper face of platform portions 26 to provide skirt portions 29 projecting therebelow. The complex shape of this cladding element is preferably formed in two portions 30, 31. These individual parts may be made in a stamping operation providing both the outside surface configuration and the recesses described hereinbelow.

The cladding material should be a metal (or alloy) susceptible of stamp forming and having a coefficient of thermal conductivity in excess of about 0.10 caL/cm. degree C. Preferably, however, the cladding material will have a coefficient of thermal conductivity in excess of about 0.5 caL/cm. sec. degree C, e.g. copper or aluminum.

Skirt portions 29 together with the underside of platform portions 26 define a gutter region 32, which accumulates cooling water nozzles 21, 22. In gutter regions 32, the accumulating liquid cools parts with which it comes in contact while it is retained until it has been accelerated to the prevailing disc rim velocity. When the cooling water in gutters 32 has been so accelerated, this water continually drains from gutter regions 32 in a generally radially outward direction along coolant passages 33 under the influence of centrifugal force to be finally discharged through the open ends 34 thereof.

The distribution of coolant passages 33 over the interface between cladding 30, 31 and spar 27 may be either in a nonuniform or a uniform arrangement depending upon the cooling requirements. Further, coolant passages 33 need not all have the same transverse cross-sectional area but may be of different sizes to accomplish specific cooling requirements. The passage of cooling water from gutter regions 32 to coolant passages 33 is, of course, controlled by the openings to passages 33 and in this manner these coolant passages serve as their own metering orifices.

Each conduit passage 33 consists of a groove recessed in sheets 30, 31 in cooperation with the surface of spar 27 to which cladding sheets 30, 31 are bonded.

Adjacent grooves recessed in the inner surface of cladding elements 30, 31 are separated by ribs 36. Prior to assembly the outer face of ribs 36 and the outer surface of spar 27 are preferably coated with a brazing metal or alloy. When the assembled coated parts are heated in a nonoxidizing atmosphere to brazing temperatures, the parts are integrally united through a bond at each rib 36. The bond between cladding elements 30, 31 and spar 27 may be made in other ways, of course, as by welding, soldering, cementing or diffusion bonding. When, for example, cladding 30, 31 is made of copper sheet, the cladding elements and the outer faces of ribs 36 and the surfaces of the spar are gold plated and then brazed together by heating under pressure in a hydrogen furnace.

Preferably, most of the surface area of each passageway 33 is made of material having a very high thermal conductivity and the cooling of the outer surface of each bucket 19 is very effective, even when the coolant liquid becomes forced to one side of each passage 33 by body forces during the rotation of the turbine rotor.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A fluid-cooled turbine bucket comprising in combination:

a. a solid inner metal spar having an anchoring root portion,

a stem portion and a transversely extending platform portion, and

b. cladding means covering said stem portion and platform portion extending over the pressure side of said stem portion, the suction side of said stem portion, and the upper face of said platform portion and projecting as a skirt below said platform portion,

1. said cladding means having a plurality of grooves open at both ends and separated by ribs, said grooves being recessed in the inner face of said cladding means and extending from below said platform portion to the distal end of said stem portion,

2. said ribs being bonded to the adjacent surfaces of said spar.

2. The fluid-cooled turbine blade as recited in claim 1 wherein the cladding means is made of a metal having a coefficient of thermal conductivity in excess of about 0. l0 cal./cm. sec. C.

3. The fluid-cooled turbine blade as recited in claim 2 wherein the cladding means has a thickness in the range of from about 0.020 inch to about 0.050 inch.

4. The fluid-cooled turbine blade as recited in claim 1 wherein the cladding means is made of a metal having a coefficient of thermal expansion in excess of about 5 caL/cm. sec. C.

5. The fluid-cooled turbine as recited in claim 1 wherein the 5 cladding means is made of copper.

UNITED STATES PATENT OFFICE CERTIFICATE OF (IQRRIXITIQN Patent No. 3 619 376 Dated November 9, 1971 Invent0r(S) Paul H. Kydd It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In claim 4, line 3, delete "expansion" and insert conductivity Signed and sealed this 6th day of February 1973.

(SEAL) Attest:

EDWARD I I.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents I QM DO1OSC No-69) USCO M-GC 60376-F'69 

1. A fluid-cooled turbine bucket comprising in combination: a. a solid inner metal spar having an anchoring root portion, a Stem portion and a transversely extending platform portion, and b. cladding means covering said stem portion and platform portion extending over the pressure side of said stem portion, the suction side of said stem portion, and the upper face of said platform portion and projecting as a skirt below said platform portion,
 1. said cladding means having a plurality of grooves open at both ends and separated by ribs, said grooves being recessed in the inner face of said cladding means and extending from below said platform portion to the distal end of said stem portion,
 2. said ribs being bonded to the adjacent surfaces of said spar.
 2. said ribs being bonded to the adjacent surfaces of said spar.
 2. The fluid-cooled turbine blade as recited in claim 1 wherein the cladding means is made of a metal having a coefficient of thermal conductivity in excess of about 0.10 cal./cm. sec. *C.
 3. The fluid-cooled turbine blade as recited in claim 2 wherein the cladding means has a thickness in the range of from about 0.020 inch to about 0.050 inch.
 4. The fluid-cooled turbine blade as recited in claim 1 wherein the cladding means is made of a metal having a coefficient of thermal expansion in excess of about 0.5 cal./cm. sec. *C.
 5. The fluid-cooled turbine as recited in claim 1 wherein the cladding means is made of copper. 